posted by Anonymous .
To reduce the loss of helium, a pressure vessel is lined with a membrane made of tantalum. The concentration of helium at the inner surface of the membrane is held constant at 4.44*10-5 kg/m3, while the concentration at the outer surface of the membrane is held constant at zero. The area of the membrane is 2.22 m2, and the diffusivity of helium in tantalum is DHe = 3.091 * 10-11 m2/s.
What must be the minimum membrane thickness that will ensure that at steady state the helium leak rate not exceed 1.11*10-6 kg/h?
Express your answer in m: